Chemical Effects of Acoustic Cavitation

A novel high-frequency, high-power, pilot-plant scale sonochemical reactor was developed and used to study the degradation of dichloromethane, trichloroethylene, phenol, and methyl orange in aqueous solutions. The degradation rates of trichloroethylene, dichloromethane, and phenol were found to exceed those of similar frequency, small-scale bench reactors by factors ranging from 2.5 to 7. The degradation of these compounds was found to be inversely related to their initial concentrations. Experiments with 10 μM methyl orange in the large reactor operating at different total volumes exhibited a linear dependence between the observed sonolytic rate constants and the applied power density. Likewise, steady-state ⋅OH (aq) in each reactor were calculated and shown to correlate with the applied power density in the vessel. Comparisons of the power density utilization between sonochemical methods and photocatalytic techniques applied to the same chemical systems show an improvement of up to two orders of magnitude of efficiency when ultrasonic irradiation is employed. The sonochemical decomposition of phenol was further studied in a bench-scale ultrasound reactor combination with ozonolysis. The addition of ozone during sonication did not affect the first-order degradation rate constants of phenol compared to the linear combination of separate sonication and ozonation experiments. However, enhancement of the degradation rates of the total organic carbon (TOC) by 43% was observed for sonolytic ozonation compared to the separate sonication and ozonolysis experiments. Complete mineralization of phenol to CO2 and H2O was only achieved using the simultaneous application of these two systems. A comparison of phenol’s TOC degradation profiles using various combinations of these two techniques reveals that the